The screening and selection of genomic libraries is one method used to identify genetic elements that confer a particular host function. In Gram negative bacteria numerous plasmid vectors have been used for construction of these libraries. Many of these vectors were derived from pUC plasmids designed to facilitate the screening for inserts or open reading frame cloning. These vectors often contain a variety of features, such as inducible or constitutive promoters followed by ribosome binding sites and start codons, the β-galactosidase gene, and, in the case of shuttle vectors, multiple replicons. These features are not ideal for the creation of stable, extra-chromosomal genomic libraries but are beneficial for expression library construction. Other features are needed for construction of these libraries.
Further, toxicity and/or instability of present vectors available for use with Gram negative bacteria are an issue. A need exists for broad-host-range vectors that can be used in a variety of Gram negative bacteria, with improved tolerance of toxicity and/or stability.